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GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

27553 results found.

  1. GRB 250628C: Fermi GBM Final Real-time Localization
  2. GRB 250628B: SVOM detection of a long burst
  3. GRB 250625A: VLT/X-shooter spectroscopic observations at the afterglow position
  4. GRB 250628A: VLT/X-shooter upper limits
  5. GRB 250628A: Swift/UVOT Upper Limits
  6. GRB 250628A: Swift-XRT refined Analysis
  7. GRB 250628A: Enhanced Swift-XRT position
  8. GRB 250628A: Swift detection of a burst
  9. GRB 250625A: Leavitt Observatory afterglow detection
  10. GRB 250625A: AbAO and INASAN Kislovodsk Optical Observations
  11. GRB 250625A: GTC/OSIRIS+ spectroscopic observations of the potential host galaxy
  12. GRB 250626A: Fermi GBM Final Real-time Localization
  13. GRB 250625A: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  14. GRB 250625A: SVOM/C-GFT upper limit in early phase
  15. GRB 250625A: GECAM-B detection
  16. GRB 250625A: Swift/UVOT Upper Limits
  17. GRB 250625A: ABObservatory afterglow detection
  18. GRB 250625A: OHP/T193 optical detection
  19. GRB 250625A: COLIBRÍ optical observations
  20. GRB 250625A: Fermi-LAT detection
  21. GRB 250625A: Swift-XRT refined Analysis
  22. GRB 250625A: JinShan optical observations
  23. GRB250625A: Fermi GBM Observation
  24. GRB 250625A: NOT z-band upper limit
  25. GRB 250625A: SVOM/VT optical confirmation
  26. GRB 250625A: SAO RAS possible optical afterglow
  27. GRB 250625A: Enhanced Swift-XRT position
  28. GRB 250625A: Swift detection of a burst
  29. GRB 250625A: Fermi GBM Final Real-time Localization
  30. GRB 250620A: AstroSat CZTI detection
  31. GRB 241018A: Maidanak optical observations
  32. GRB 250620C: AstroSat CZTI detection
  33. GRB 250624A: Fermi GBM Final Real-time Localization
  34. sb25061207/GRB 250612D - SVOM/ECLAIRs refined analysis
  35. GRB 250623A: Fermi GBM Final Real-time Localization
  36. GRB 250521A: VZLUSAT-2 detection
  37. Konus-Wind detection of GRB 250620C
  38. IPN triangulation of GRB 250620C (long/bright)
  39. GRB 250621B: SVOM/GRM detection of a possible magnetar X-ray burst
  40. GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  41. GRB 250621A: Fermi GBM Final Real-time Localization
  42. GRB 250620A: Swift/BAT-GUANO subthreshold detection of a possibly short burst
  43. GRB 250620C: Fermi GBM Final Real-time Localization
  44. GRB 250620B: Fermi GBM Final Real-time Localization
  45. GRB 250620A: Fermi GBM Final Real-time Localization
  46. EP-WXT trigger 01709179036: a new outburst of GRS 1739-278
  47. GRB 250617B: Nickel telescope optical observations
  48. GRB 250619B: Fermi GBM Final Real-time Localization
  49. GRB 250615A: Kilonova-Catcher optical upper limits
  50. GRB 250619A: Fermi GBM Final Real-time Localization
  51. GRB 250617B: Assy AZT-20 Optical Observations
  52. GRB 250612A / Swift J1643.6−3854: Swift-BAT refined analysis
  53. GRB 250615A/EP250615a: FTW optical and NIR observations
  54. sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
  55. GRB 250617B: Swift/UVOT Detection
  56. GRB 250617B: Kilonova-Catcher optical afterglow detection
  57. GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
  58. GRB 250617B: NOT NIR observations of the afterglow
  59. GRB 250617B: Swift-XRT refined Analysis
  60. GRB 250617B: SVOM/VT optical observation
  61. GRB 250617B: NUTTelA-TAO early time optical observations
  62. GRB 250617B: GOTO optical upper limit
  63. GRB 250617B: Enhanced Swift-XRT position
  64. GRB 250617B: Fermi GBM Final Localization
  65. GRB 250617B: Ondrejov D50 optical afterglow detection
  66. GRB 250617B: Swift detection of a burst with an optical counterpart
  67. GRB 250617A: Fermi GBM Final Real-time Localization
  68. IPN triangulation of GRB 250612C (short/hard)
  69. EP#01709178975: Swift-XRT counterpart detection
  70. Konus-Wind detection of GRB 250615A / EP250615a
  71. GRB 250615A / EP250615a: AstroSat CZTI detection
  72. GRB 250615A: COLIBRÍ optical upper limit
  73. GRB 250615A: DDOTI Optical Upper Limit
  74. GRB 250615A: Swift/UVOT Upper Limits
  75. Konus-Wind detection of GRB 250612C (short/hard with extended emission)
  76. GRB 250615A: Swift-XRT refined Analysis
  77. EP250615a/GRB 250615A: EP-WXT detection of a fast X-ray transient
  78. EP-WXT trigger 01709178875: confirmation of a stellar flare by BOOTES-6
  79. GRB 250615A: Enhanced Swift-XRT position
  80. GRB 250615A: Prompt enhanced Swift-XRT position
  81. GRB 250615A: Swift detection of a burst
  82. GRID detection of GRB 250612C
  83. sb25061207: Mephisto optical upper limits
  84. IceCube alert 141029_8144692 retraction
  85. GRB 250614A: Fermi GBM Final Real-time Localization
  86. EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
  87. sb25061218: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  88. sb25061218: Swift-XRT observations
  89. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
  90. sb25061207: EP-FXT follow-up observation and afterglow candidate
  91. sb25061218: SVOM detection of a X-ray transient
  92. sb25061207: Swift-XRT observations
  93. EP 250612a: AST3-3 Yaoan Optical Observation
  94. GRB 250610B: Swift-XRT refined Analysis
  95. GRB 250612C: Fermi GBM Final Real-time Localization
  96. GRB 250612B (250612519/771424081): Fermi GBM Final Localization
  97. GRB 250612B: BALROG localization (Fermi Trigger 771424081 / GRB 250612519)
  98. EP250612a: Einstein Probe detection of an X-ray transient
  99. sb25061207: SVOM detection of a X-ray transient
  100. EP250610a: continuous follow-up observations with EP-FXT

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